Lithium ion cells have a positive electrode (cathode), a negative electrode (anode) and a porous separator disposed in between. The positive and negative electrodes each comprise a material into which lithium ions (Li+) can be intercalated and out of which they can be deintercalated again, reversibly. The intercalation and deintercalation for lithium ions takes place in the presence of an electrolyte comprising a conductive lithium salt and at least one electrolyte solvent.
In most lithium ion cells both in the consumer sector, for example in cell phones, MP3 players or power tools, and in the automotive sector, for example in electrical vehicles and hybrid vehicles, the conductive lithium salt used is lithium hexafluorophosphate (LiPF6). In order to dissolve the conductive lithium salt, ethylene carbonate (EC) is present in virtually all electrolytes currently used for lithium ion cells. The separator used is usually a polyethylene or polypropylene separator.